The present invention relates to a pulse signal control circuit and more particularly to a high frequency pulse signal control circuit for obtaining a high voltage pulse data signal containing a high frequency pulse train in response to a low voltage data signal.
An example of use for such pulse signal control circuit is a generator of high-voltage and high-frequency pulses for driving an alternating current (AC) drive type plasma display panels or the like.
In a driving circuit for an AC plasma display panel, it is desired to generate a high frequency pulse train with a good rise-time characteristic. Such driving circuit is disclosed in U.S. Pat. No. 4,359,648 issued on Nov. 16, 1982 to the same applicants of the present invention. This circuit comprises an amplifier circuit for amplifying a pulse data input signal. The amplifier circuit includes, a switching transistor which comprises an NPN type transistor with its emitter electrode grounded and its collector electrode connected to a high voltage source (+Vo) via a resistor which acts as a collector resistor for the switching transistor. The amplifier circuit further includes a buffer transistor which comprises NPN type transistor with its collector electrode connected directly to the source (+Vo) whereas its base electrode is connected to the juncture of the collector resistor with the collector electrode of the switching transistor. A buffer diode is connected across the base and emitter electrodes of the buffer transistor. In order to improve a rise-time characteristic of a high frequency pulse train at an output terminal connected to the emitter electrode of the buffer transistor, according to the above mentioned U.S. Patent, a preamplified high frequency pulse is normally applied to the collector electrode of the switching transistor via a diode. The phase of the preamplified high frequency pulse train is opposite to that of input pulse train applied to the base electrode of the switching transistor. Such preamplified high frequency pulse train is obtained by amplifying a high frequency input pulse train which is to be supplied to the base electrode of the switching transistor via a gate circuit and an inverter circuit. According to the above described circuit, since the preamplified high frequency pulse train can be directly applied to the base electrode of the buffer transistor when the switching transistor is turned off, the rise-time characteristic of the output pulse train is greatly improved.
However, since a turn-off characteristic of the switching transistor is poor due to the minority carrier storage effect, a large current would flow at every initial moment of that an input pulse changes from a high to low levels at the base electrode of the switching transistor. Although the turn-off characteristic of the switching transistor can be improved by supplying an input pulse to the gate thereof via a so-called speed-up capacitor, such improved circuit is not preferable to reduce it into a monolithic integrated circuit owing to the fact that the capacitor requires a large area. Especially, for the AC plasma display panel to be driven in a scanning mode, a large number of scanning electrodes require the same number of driver circuits and thus the presence of a large number of speed-up capacitors is an obstacle to reduce it into a monolithic integrated circuit.